Photoresist composition and method of manufacturing a thin-film transistor substrate using the same

ABSTRACT

A photoresist composition includes about 100 parts by weight of resin mixture including novolak resin and acryl resin and about 10 parts to about 50 parts by weight of naphthoquinone diazosulfonic acid ester. A weight-average molecular weight of the novolak resin is no less than about 30,000. A weight-average molecular weight of the acryl resin is no less than about 20,000. A content of the acryl resin is about 1% to about 15% by weight based on a total weight of the resin mixture. When a photoresist film formed using the photoresist composition is heated, a profile variation of the photoresist composition is relatively small. Therefore, a residual photoresist film has a uniform thickness, and a short circuit and/or an open defect in a TFT substrate may be reduced.

BRIEF EXPLANATION OF THE DRAWINGS

FIGS. 1A to 1D are pictures showing a photoresist pattern flowing when baked;

FIGS. 2A to 2C are pictures illustrating the photoresist pattern formed using the photoresist composition of Example 1;

FIGS. 3A to 3C are pictures illustrating the photoresist pattern formed using the photoresist composition of Comparative Example 1;

FIGS. 4A to 4C are pictures illustrating the photoresist pattern formed using the photoresist composition of Comparative Example 2;

FIG. 5 is a plan view illustrating a TFT substrate according to an exemplary embodiment of the present invention;

FIGS. 6 and 7 are cross-sectional views taken along a line II-II′ and a line III-III′ of FIG. 1;

FIGS. 8, 21 and 24 are plan views illustrating a method of manufacturing a TFT substrate according to an exemplary embodiment of the present invention;

FIGS. 9 and 10 are cross-sectional views taken along a line V-V′ and a line VI-VI′ of FIG. 8;

FIGS. 14 to 20 are cross-sectional views illustrating a method of manufacturing a TFT substrate according to an exemplary embodiment of the present invention.

FIGS. 22 and 23 are cross-sectional views taken along a line XVIII-XVIII′ and a line XIX-XIX′ of FIG. 21;

FIGS. 25 and 26 are cross-sectional views taken along a line XXI-XXI′ and a line XXII-XXII′ of FIG. 24.

EXPLANATION ON CHIEF REFERENCE NUMERALS OF DRAWINGS

52, 54: photoresist pattern

83: overpass

110: base substrate

120: gate layer

121: gate line

124: gate electrode

131: storage electrode line

133 a, 133 b: storage electrode

140: gate insulating layer

150: amorphous silicon layer

154: semiconductor layer

160: n⁺ amorphous silicon layer

171: data line

173: source electrode

175: drain electrode

180: passivation layer

191: pixel electrode

81, 82 contact assistant

DETAILED DESCRIPTION OF THE INVENTION PURPOSE OF THE INVENTION THE ART TO WHICH THE INVENTION PERTAINS AND THE PRIOR ART

The present invention relates to a photoresist composition and a method of manufacturing a thin-film transistor substrate using the photoresist composition. More particularly, the present invention relates to a photoresist composition having a relatively high heat-resistance to reduce a profile variation of a photoresist film formed using the photoresist composition when heated, and a method of manufacturing a thin-film transistor substrate using the photoresist composition.

In general, a liquid crystal display apparatus is manufactured through a five-mask process. However, a four-mask process has been developed in order to reduce manufacturing costs and to improve a manufacturing efficiency. In the four-mask process, it is preferable that a profile of a photoresist film formed by coating a photoresist composition on a substrate is relatively large in order to easily progress the four-mask process. When the profile of the photoresist film is relatively large, a design margin is reduced, and an etching process is easily performed. When a photoresist pattern formed from a conventional photoresist composition is heated at a temperature of no less than about 125° C., the photoresist pattern flows so that an angle between a side surface of the photoresist pattern and an upper surface of a substrate, on which the photoresist pattern is formed, becomes no more than about 40 degrees.

FIGS. 1A to 1D are pictures showing a photoresist pattern flowing when baked.

Particularly, FIG. 1A is an SEM picture showing a process developing the photoresist pattern, and FIG. 1B is an SEM picture showing an initial profile of the photoresist pattern after developed. An angle between a side surface of the photoresist pattern and an upper surface of a substrate, on which the photoresist pattern is formed, is about 50 degrees.

After the developing process, the photoresist pattern is post-baked and hard-baked in order to increase an etching-resistance of the photoresist pattern. When the photoresist pattern is heated, photoresist pattern reflows so that an angle between the side surface of the photoresist pattern and the upper surface of the substrate, on which the photoresist pattern is formed, becomes about 30 degrees to about 35 degrees.

FIG. 1C is an SEM picture showing the photoresist pattern reflowed through a hard-baking process, and FIG. 1D is an SEM picture showing a profile of the photoresist pattern that has reflown through a hard-baking process.

When the photoresist pattern reflows, a channel length becomes narrower as shown in FIG. 1D. Thus, a time for etching is increased, and a skew is increased. Furthermore, the photoresist pattern is sensitive to a temperature variation of the equipments so that a shape of the photoresist pattern depends on a temperature variation of a manufacturing apparatuses. Thus, a thickness variation of the photoresist pattern is increased so that a short circuit is caused in an area where the photoresist pattern is relatively thick, and an open defect is caused in an area where the photoresist pattern is relatively thin.

TECHNICAL OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide a photoresist composition having a relatively high heat-resistance so that reflowing during the baking process is minimized.

It is another object of the present invention to provide a method of manufacturing a thin-film transistor substrate using the above-mentioned photoresist composition so that the etch skew and the uniformity of the pattern are improved to reduce the short and open defects.

CONTRUCTION AND OPERATION OF THE INVENTION

In one aspect of the present invention, a photoresist composition includes about 100 parts by weight of resin mixture including a novolak resin and an acryl resin and about 10 parts to about 50 parts by weight of naphthoquinone diazosulfonic acid ester.

The weight-average molecular weight of the novolak resin may be no less than about 30,000. The weight-average molecular weight of the acryl resin may be no less than about 20,000. The content of the acryl resin may be about 1% to about 15% by weight based on a total weight of the resin mixture.

In another aspect of the present invention, there is provided a method of manufacturing a thin-film transistor substrate. In the method, a gate line is formed on a base substrate. A gate insulating layer, a semiconductor layer and a data layer are sequentially formed on the gate line and the base substrate. A photoresist composition is coated on the data layer to form a photoresist film. The photoresist composition includes about 100 parts by weight of resin mixture including novolak resin and acryl resin and about 10 parts to about 50 parts by weight of naphthoquinone diazosulfonic acid ester. The photoresist film is patterned to form a photoresist pattern. The data layer is firstly etched by using the photoresist pattern as a mask. The semiconductor layer is etched by using an etched data layer. The photoresist pattern is heated. The data layer is secondly etched by using a heated photoresist pattern as a mask.

The weight-average molecular weight of the novolak resin may be no less than about 30,000. The weight-average molecular weight of the acryl resin may be no less than about 20,000. The content of the acryl resin may be about 1% to about 15% by weight based on a total weight of the resin mixture.

According to the above, a photoresist composition has a relatively high heat-resistance. Thus, when a photoresist film formed using the photoresist composition is heated, a profile variation of the photoresist film is relatively small. Furthermore, a short circuit and/or an open defect in a TFT substrate may be reduced.

Hereinafter, the photoresist composition according to an exemplary embodiment of the present invention will be explained more fully.

Photoresist Composition

A photoresist composition is provided. The photoresist composition is a positive photoresist composition and has a relatively high heat-resistance. The photoresist composition includes about 100 parts by weight of a resin mixture and about 10 parts to about 50 parts by weight of naphthoquinone diazosulfonic acid ester.

The resin mixture includes a novolak resin and an acryl resin.

The novolak resin may be synthesized by reacting a phenol-based compound and an aldehyde-based compound. Examples of the phenol-based compound may include phenol, para-cresol, meta-cresol, etc. These can be used alone or in a mixture thereof. Examples of the aldehyde-based compound include formaldehyde, benzaldehyde, acetaldehyde, etc. An acid catalyst is used for reacting the phenol-based compound and the aldehyde-based compound. For example, the acid catalyst may be oxalic acid. The novolak resin may include a plurality of novolak resins different from each other to improve a residual ratio and a sensitivity of the photoresist composition.

The weight-average molecular weight of the novolak resin may be no less than about 30,000.

The acryl resin is a copolymer synthesized from monomers, such as methyl methacrylate, ethyl methacrylate, methacrylic acid, styrene, benzylacrylate, acrylic acid, etc. For example, the acryl resin may be synthesized from at least two kinds of the monomers.

The weight-average molecular weight of the acryl resin may be no less than about 20,000.

The content of the acryl resin may be about 1% to about 15% by weight based on a total weight of the resin mixture, and preferably about 5% to about 12% by weight.

Examples of the naphthoquinone diazosulfonic acid ester as a photosensitive compound may include 2,3,4-trihydroxy benzophenone ester of naphthoquinone 1,2-diazo-5-sulfonic acid, 2,3,4,4′-tetrahydroxy benzophenone ester of naphthoquinone 1,2-diazo-5-sulfonic acid, etc.

The content of the naphthoquinone diazosulfonic acid ester may be about 10 parts to about 50 parts by weight with respect to about 100 parts by weight of the resin mixture. When the content of the naphthoquinone diazosulfonic acid ester is less than about 10 parts by weight, a thickness of a portion of a photoresist, which is not exposed to light, may be excessively reduced. When the content of the naphthoquinone diazosulfonic acid ester is more than about 50 parts by weight, a sensitivity of the photoresist composition may be reduced, and residue of the photoresist may remain after being developed. Preferably, the content of the naphthoquinone diazosulfonic acid ester may be about 20 parts to about 40 parts by weight with respect to about 100 parts by weight of the resin mixture.

The photoresist composition may be mixed with an organic solvent. Examples of the organic solvent may include ketone, propylene glycol monomethyl ether acetate, benzyl alcohol, gamma-butyrolactone, ethyl lactate, n-buthyl acetate, methoxy methyl propionate, an alcohol and a derivative thereof, etc. Examples of the ketone include 2-hepanone, chlorohexanone, etc. Examples of the alcohol and the derivative thereof include ethylene glycol, ethylene glycol monoalkyl ether, monopropyl ether, monobutyl ether, diethylene glycol, monopropyl ether of monoacetic acid, etc. These can be used alone or in a mixture thereof.

The photoresist composition may further include an additive such as a surfactant, etc.

The photoresist composition is described more fully hereinafter with reference to the accompanying examples. This invention may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein.

EXAMPLE 1

A mixture including formaldehyde, metha-cresol and para-cresol were polymerized in the presence of an oxalic acid as a catalyst to prepare a novolak resin. A ratio of the metha-cresol to para-cresol was about 60 to about 40 by weight. A weight-average molecular weight of the novolak resin was about 38,000. The novolak resin was mixed with an acryl resin, of which a weight-average molecular weight was about 28,000, such that a content of the acryl resin was about 10% by weight based on a total weight of a resin mixture. The resin mixture was mixed with about 20 parts by weight of 2,3,4,4′-tetrahydroxy benzophenone ester of naphthoquinone 1,2-diazo-5-sulfonic acid with respect to about 100 parts by weight of the resin mixture to prepare a mixture. The mixture was solved in about 200 parts by weight of a solvent mixture including propylene glycol monomethyl ether acetate and benzyl alcohol to prepare a solution. The solution was filtered by a filter, of which a diameter was about 0.2 to prepare a photoresist composition.

COMPARATIVE EXAMPLE 1

A mixture including formaldehyde metha-cresol and para-cresol were polymerized in the presence of an oxalic acid as a catalyst to prepare a novolak resin. A ratio of the metha-cresol to para-cresol was about 60 parts by weight to about 40 parts by weight. A weight-average molecular weight of the novolak resin was about 12,000. The novolak resin mixed with about 20 parts by weight of 2,3,4,4′-tetrahydroxy benzophenone ester of naphthoquinone 1,2-diazo-5-sulfonic acid with respect to about 100 parts by weight of thus obtained mixture. The mixture was solved in about 200 parts by weight of a solvent mixture including propylene glycol monomethyl ether acetate and benzyl alcohol to prepare a solution. The solution was filtered by a filter, of which a diameter was about 0.2 to prepare a photoresist composition.

COMPARATIVE EXAMPLE 2

A mixture including formaldehyde metha-cresol and para-cresol were polymerized in the presence of an oxalic acid as a catalyst to prepare a novolak resin. A ratio of the metha-cresol to para-cresol was about 60 parts by weight to about 40 parts by weight. A weight-average molecular weight of the novolak resin was about 27,000. The novolak resin mixed with about 20 parts by weight of 2,3,4,4′-tetrahydroxy benzophenone ester of naphthoquinone 1,2-diazo-5-sulfonic acid with respect to about 100 parts by weight of thus obtained mixture. The mixture was solved in about 200 parts by weight of a solvent mixture including propylene glycol monomethyl ether acetate and benzyl alcohol to prepare a solution. The solution was filtered by a filter, of which a diameter was about 0.2 to prepare a photoresist composition.

Experiment for Evaluation of Photoresist Pattern

A plurality of photoresist patterns was formed by using the photoresist compositions of Example 1, Comparative Examples 1 and 2. A thickness deviation (A), a profile and a skew of each of the photoresist patterns were measured. Particularly, an inclination (B) of the photoresist pattern before heated, an inclination (C) of the photoresist pattern heated at a temperature of about 130° C. and an inclination (D) of the photoresist pattern heated at a temperature of about 135° C. were measured. Furthermore, a skew (E) after firstly etched and a skew (F) after firstly etched and active-etched and etched back were measured. Thus obtained results are illustrated in following Table 1. TABLE 1 Profile (°) Skew (μm) A (Å) B C D E F Example 1 2000 46.6 46.1 45.2 2.0 2.52 Comparative 6000 41 31 29 2.7 3.5 Example 1 Comparative 2500 43 37 35 2.2 3.4 Example 2

Referring to Table 1, an inclination variation of the photoresist pattern formed using the photoresist composition of Example 1 before and after heated was relatively small. Thus, the skew was reduced in comparison with Comparative Examples 1 and 2

FIGS. 2A, 2B and 2C are SEM pictures illustrating the photoresist pattern formed using the photoresist composition of Example 1. Particularly, FIG. 2A is an SEM picture illustrating the photoresist pattern before being hard-baked, and FIG. 2B is an SEM picture illustrating the photoresist pattern after being hard-baked, and FIG. 2C is an SEM picture illustrating the photoresist pattern after being dry-etched. FIGS. 3A, 3B and 3C are SEM pictures illustrating the photoresist pattern formed using the photoresist composition of Comparative Example 1. FIGS. 4A, 4B and 4C are SEM pictures illustrating the photoresist pattern formed using the photoresist composition of Comparative Example 2.

Referring to FIGS. 2A to 4C, it can be noted that the photoresist pattern formed using the photoresist composition of Example 1 has a relatively great heat-resistance so that a shape variation of the photoresist pattern is relatively small when heated.

A method of manufacturing a thin-film transistor (TFT) substrate according to an exemplary embodiment of the present invention is described more fully hereinafter with reference to the accompanying drawings.

Method of Manufacturing a Thin-Film Transistor Substrate

A TFT substrate and a method of manufacturing the TFT substrate are described with reference to FIGS. 5, 6 and 7.

FIG. 5 is a plan view illustrating a TFT substrate according to an exemplary embodiment of the present invention. FIG. 6 is a cross-sectional view taken along a line II-II′ of FIG. 5. FIG. 7 is a cross-sectional view taken along a line III-III′ of FIG. 5.

A plurality of gate lines 121 and a plurality of storage electrode lines 131 are formed on a base substrate 110. Examples of the base substrate 110 include glass, and a polymer, etc.

The gate line 121 delivers a gate signal and extends in a row direction. Each of the gate lines 121 includes a plurality of gate electrodes 124 and an end 129 electrically connected to an external driving circuit or a layer formed on or under the gate line 121. A gate driving circuit (not shown) generating the gate signal may be formed on a flexible printed circuit film (not shown) coupled to the base substrate 110. Alternatively, the gate driving circuit may be directly formed on the base substrate 110 or may be integrally formed with the base substrate 110. When the gate driving circuit is integrally formed with the base substrate 110, the gate driving circuit may be directly connected to the gate line 121.

A predetermined voltage is applied to the storage electrode line 131. The storage electrode line 131 includes a branch substantially parallel with the gate line 121, a first storage electrode 133 a and a second storage electrode 133 b extended from the branch. Each of the storage electrode lines 131 is disposed between two of the gate lines 121 adjacent to each other. Each of the storage electrodes 133 a and 133 b include a secured end connected to the branch and a free end opposite to the secured end. A free end of the first storage electrode 133 a has a size larger than a free end of the second storage electrode 133 b and has a first branch straightly extended and a second branch bended. The storage electrode line 131 may have a various shape.

For example, each of the gate lines 121 and the storage electrode lines 131 may include aluminum (Al), silver (Ag), copper (Cu), chrome (Cr), tantalum (Ta), titanium (Ti), molybdenum (Mo), an alloy thereof, etc. Furthermore, each of the gate lines 121 and the storage electrode lines 131 may include a multiple layer that includes a first layer and a second layer having physical characteristics different from the first layer. For example, a first layer may include aluminum, silver, copper, an alloy thereof, etc. in order to reduce a signal delay and/or a voltage drop. A second layer may include a metal such as chrome, tantalum, titanium, molybdenum, an alloy thereof, etc., which is advantageously in contact characteristics with a transparent conductive material, such as indium tin oxide (ITO), indium zinc oxide (IZO), etc. Particularly, each of the gate lines 121 and the storage electrode lines 131 may include a multiple layer such as chrome/aluminum layer, aluminum/molybdenum layer, etc. Each of the gate lines 121 and the storage electrode lines 131 may include a various conductive material besides the above.

A side surface of each of the gate lines 121 and the storage electrode lines 131 is inclined with respect to an upper surface of the base substrate 110, for example, by about 30 degrees to about 80 degrees.

A gate insulating layer 140 is formed on the gate lines 121 and the storage electrode lines 131. Examples of the gate insulating layer 140 include silicon nitride (SiNx), silicon oxide (SiOx), etc.

A plurality of semiconductor layers 151 is formed on the gate insulating layer 140. For example, the semiconductor layer 151 includes hydrogenated amorphous silicon. The semiconductor layer 151 extends in a column direction and has a protrusion layer 154 covering the gate electrode 124. The semiconductor layer 151 covers the gate line 12 and the storage electrode line 131.

A first ohmic contact layer 161 having a liner shape and a second ohmic contact layer 165 having an island shape are formed on each of the semiconductor layer 151. Examples of the first and second ohmic contact layers 161 and 165 may include silicide, n⁺ hydrogenated amorphous silicon into which n⁺ impurities such as phosphorous (P) are implanted, etc. The first ohmic contact layer 161 has a protrusion layer 163. Both the protrusion layer 163 of the first ohmic contact layer 161 and the second ohmic contact layer 165 are disposed on the protrusion layer 154 of the semiconductor layer 151.

A side surface of each of the semiconductor layer 151 and the first and second ohmic contact layers 161 and 165 is inclined with respect to the upper surface of the base substrate 110, for example, by about 30 degrees to about 80 degrees.

A plurality of data lines 171 and a plurality of drain electrodes 175 are formed on the first and the second ohmic contact layers 161 and 165.

The data line 171 delivers a data signal and extends in the column direction to cross the gate line 121. Each of the data lines 171 crosses the storage electrode line 131 and is disposed between the first and the second storage electrodes 133 a and 133 b. Each of the data lines 171 includes a source electrode 173 and an end 179 electrically connected to an external driving circuit or a layer formed on or under the data line 171. A data driving circuit (not shown) generating the data signal may be formed on a flexible printed circuit film (not shown) coupled to the base substrate 110. Alternatively, the data driving circuit may be directly formed on the base substrate 110 or may be integrally formed with the base substrate 110. When the data driving circuit is integrally formed with the base substrate 110, the data driving circuit may be directly connected to the data line 171.

The drain electrode 175 is spaced apart from the data line 171 and faces the source electrode 173. Each of the drain electrodes 175 has a first end having a bar-shape and a second end having a size larger than the first end. The first end is surrounded by the source electrode 173, and the second end overlaps with the storage electrode line 131.

A TFT includes the gate electrode 124, the source electrode 173, the drain electrode 175 and the protrusion layer 154 of the semiconductor layer 151. A channel layer is formed at the protrusion layer 154 of the semiconductor layer 151 between the source electrode 173 and the drain electrode 175.

For example, examples of the data lines 171 and the drain electrodes 175 may include a refractory metal or an alloy thereof, etc. Furthermore, each of the data lines 171 and the drain electrodes 175 may include a multiple layer having a refractory metal layer and a low-resistance metal layer. Particularly, the multiple layer may include a lower layer including chrome and/or molybdenum and an upper layer including aluminum. Alternatively, the multiple layer may include a lower layer including molybdenum, a middle layer including aluminum and an upper layer including molybdenum. Each of the data lines 171 and the drain electrodes 175 may include a various conductive material besides the above.

A side surface of each of the data lines 171 and the drain electrodes 175 is inclined with respect to the upper surface of the base substrate 110, for example, by about 30 degrees to about 80 degrees.

The first ohmic contact layer 161 is disposed between the semiconductor layer 151 and the data line 171 to reduce a contact resistance, and the second ohmic contact layer 165 is disposed between the semiconductor layer 151 and the drain electrode 175 to reduce a contact resistance.

The semiconductor layer 151 except for the protrusion layer 154 has a substantially same shape as the data line 171, the drain electrode 175 and the first and the second ohmic contact layers 161 and 165 when viewed from a plan view. Particularly, the semiconductor layer 151 is overlapped with the data line 171, the drain electrode 175 and the first and the second ohmic contact layers 161 and 165. A portion of the semiconductor layer 151 between the source electrode 173 and the drain electrode 175 is exposed. Practically, the semiconductor layer 151 may have a size larger than the data line 171 and the drain electrode 175 in view of a manufacturing process.

A passivation layer 180 covers on the data line 171, a drain electrode 175 and the exposed portion of the semiconductor layer 151.

Examples of a material that may be used for the passivation layer 180 include an organic insulating material, a low-dielectric insulating material, a ceramic insulating material, such as silicon nitride, silicon oxide, etc. For example, a dielectric constant of each of the organic insulating material and the low-dielectric insulating material may be no less than about 4.0. Particularly, the low-dielectric insulating material may include amorphous silicon formed through a plasma enhanced chemical vapor deposition (PECVD) method. The organic insulating material may have photosensitive characteristics. A surface of the passivation layer 180 may be substantially flat. The passivation layer 180 may include a lower ceramic layer and an upper organic layer in order to have great insulating characteristics without damaging the exposed portion of the semiconductor layer 151.

A plurality of contact holes 182 and 185 is formed at the passivation layer 180 to expose an end 179 of the data line 171 and the drain electrode 175. Furthermore, a plurality of contact holes 181 is formed through the passivation layer 180 and the gate insulating layer 140 to expose an end 129 of the gate line 121, and a plurality of contact holes 183 a and 183 b is formed through the passivation layer 180 and the gate insulating layer 140 to expose a portion of the storage electrodes 133 a and 133 b and a portion of the storage electrode line 131.

A plurality of pixel electrodes 191, a plurality of overpasses 83, a plurality of contact assistants 81 and 82 are formed on the passivation layer 180. Each of the pixel electrodes 191, the overpasses 83 and the contact assistants 81 and 82 may include a transparent conductive material, such as ITO, IZO, etc., and/or a reflective metal such as aluminum, silver, an alloy thereof, etc.

The pixel electrode 191 is electrically connected to the drain electrode 175 through the contact hole 185, and a data voltage is applied to the pixel electrode through the drain electrode 175. The pixel electrode 191, to which the data voltage is applied, forms an electric field with a common electrode (not shown), to which a common voltage is applied, to control alignments of liquid crystal molecules in a liquid crystal layer (not shown) between the pixel electrode 191 and the common electrode. Particularly, the pixel electrode 191 and the common electrode forms a liquid crystal capacitor to maintain a voltage level of the electric field after the TFT is turned off.

The pixel electrode 191 overlaps with the storage electrodes 133 a and 133 b and the storage electrode line 131. The pixel electrode 191, the drain electrode 171 and the storage electrode line 131 form a storage capacitor to maintain the voltage level of the electric field.

The contact assistants 81 and 82 are respectively connected to the end 129 of the gate line 121 and the end 179 of the data line 171 through the contact holes 181 and 182. The contact assistants 81 and 82 reinforces an adhesion between an external apparatus and each of the end 121 of the gate line 121 and end 179 of the data line 171 and protects the end 121 of the gate line 121 and end 179 of the data line 171.

The overpass 83 crosses the gate line 121 and is electrically connected to the storage electrode line 131 and the second storage electrode 133 b through the contact holes 183 a and 183 b. The storage electrodes 133 a and 133 b, the storage electrode line 131 and the overpass 83 may be used for repairing defects of the TFT substrate.

FIGS. 8, 21 and 24 are plan views illustrating a method of manufacturing a TFT substrate according to an exemplary embodiment of the present invention. FIG. 9 is a cross-sectional view taken along a line V-V′ of FIG. 8, and FIG. 10 is cross-sectional view taken along a line VI-VI′ of FIG. 8. FIGS. 11 to 20 are cross-sectional views illustrating a method of manufacturing a TFT substrate according to an exemplary embodiment of the present invention. FIG. 22 is a cross-sectional view taken along a line XVIII-XVIII′ of FIG. 21. FIG. 23 is a cross-sectional view taken along a line XIX-XIX′ of FIG. 21. FIG. 25 is a cross-sectional view taken along a line XXI-XXI′ of FIG. 24. FIG. 26 is a cross-sectional view taken along a line XXII-XXII′ of FIG. 24.

A metal layer including molybdenum is formed on a base substrate. The metal layer is etched through a wet-etching process to form a plurality of gate lines 121 and a plurality of storage electrode lines 131. Each of the gate lines 121 has a gate electrode 124, and each of the storage electrode lines 131 has a first storage electrode 133 a and a second storage electrode 133 b.

Referring to FIGS. 11 and 12, a gate insulating layer 140, an amorphous silicon layer 150 and an n⁺ amorphous silicon layer 160, into which n⁺ impurities such as phosphorous are implanted at a high concentration, are formed on the gate line 121 and the storage electrode line 131 through a PECVD method. The amorphous silicon layer 150 may include hydrogenated amorphous silicon, and the n⁺ amorphous silicon layer 160 may include silicide, n⁺ amorphous silicon, into which n⁺ impurities such as phosphorous are implanted at a high concentration, etc.

A data layer 170 including molybdenum is formed on the n⁺ amorphous silicon layer 160 through a sputtering process.

A photoresist film is formed on the data layer 170 through a spin-coating method.

A photoresist composition is coated on the data layer 170 to form the photoresist film. The photoresist composition includes about 100 parts by weight of a resin mixture and about 10 parts to about 50 parts by weight of naphthoquinone diazosulfonic acid ester. The resin mixture includes a novolak resin and an acryl resin. A content of the acryl resin may be about 1% to about 15% by weight based on a total weight of the resin mixture. A weight-average molecular weight of the novolak resin may be no less than about 30,000. A weight-average molecular weight of the acryl resin may be no less than about 20,000. The photoresist composition may further include an organic solvent.

Referring to FIGS. 11 and 12, the photoresist film is exposed to light and developed to form a first photoresist pattern 52 and a second photoresist pattern 54 thinner than the first photoresist pattern 52.

After the photoresist is developed, the first and the second photoresist patterns 52 and 54 are not heated through a post-baking process. The post-baking process may reflow the first and the second photoresist patterns 52 and 54 to change a profile of each of the first and the second photoresist patterns 52 and 54. When the profile is changed, a following etching process may be hindered and a failure in a TFT may be caused.

Thus, the following etching process is performed without a heating process.

Hereinafter, an area ‘A’ corresponds to a data line, a storage electrode, a storage electrode line, a source electrode and a drain electrode. Furthermore, an area ‘B’ corresponds to a channel layer, and an area ‘C’ corresponds to a remained area except for the areas ‘A’ and ‘B’.

The photoresist film is etched to form the first photoresist pattern 52 in the area ‘A’ and the second photoresist pattern 54 in the area ‘B’ and to remove a portion of the photoresist film in the area ‘C’. The first photoresist pattern 52 is thicker than the second photoresist pattern 54. A thickness ratio of the first photoresist pattern 52 to the second photoresist pattern 54 may be varied in view of a manufacturing process. For example, a thickness of the second photoresist pattern 54 may be no more than about 50% of a thickness of the first photoresist pattern 52.

For example, the first photoresist pattern 52 and the second photoresist pattern 54 may be formed using a mask having a transparent area, a light blocking area and a semi-transparent area. The semi-transparent area may have a slit pattern, a lattice pattern, etc. When the semi-transparent area has a plurality of slits, a distance between the slits and a width of each of the slits may be smaller than a resolution of an exposure used for an etching process.

Referring to FIGS. 15 and 16, the data layer in the area ‘C’ is removed using the first photoresist pattern as a mask through a wet-etching process to form a first data pattern 171, a second data pattern 174 and a third data pattern 179.

The amorphous silicon layer 150 and the n⁺ amorphous silicon layer 160 in the area ‘C’ is dry-etched using the first, second and third data patterns 171, 174 and 179 as masks to form a first amorphous silicon layer 151, a second amorphous silicon layer 154, a first n⁺ amorphous silicon layer 161 and a second n⁺ amorphous silicon layer 164.

Referring to FIGS. 17 and 18, the second photoresist pattern 54 in the area ‘B’ is removed through an etching-back process. The thickness of the first photoresist pattern 52 is reduced by the thickness of the second photoresist pattern 54. Furthermore, ends of each of the first, second and third data patterns 171, 174 and 179 are exposed.

Referring to FIGS. 19 and 20, the first photoresist pattern 52 is heated at a temperature of about 100° C. to about 150° C. to reflow.

The photoresist composition has a relatively high heat-resistance so that a profile of each of the photoresist patterns 52 and 54 formed using the photoresist composition is not substantially varied before and after heated.

Referring to FIGS. 21 to 23, the second data pattern 174 is etched by using the first photoresist pattern 52 as a mask to form a source electrode 173 and a drain electrode 175 and to expose the second n⁺ amorphous silicon layer 164 between the source electrode 173 and the drain electrode 175.

Here, the second data pattern 174 may be etched through a dry-etching process or a wet-etching process.

The ends of each of the first to the third data patterns 171, 174 and 179 correspond to ends of the first resist pattern 52. Thus, when the second data pattern 174 is etched through a dry-etching process, a portion of each of the first to the third data patterns 171, 174 and 179, which is over-etched, may be relatively small. Thus, a portion of each of the first and the second n⁺ amorphous silicon layers 161 and 164, which is exposed, may be relatively small.

An adhesion between the first photoresist pattern 52 and the ends of each of the first to third data patterns 171, 174 and 179 is relatively strong. Furthermore, a stress caused by flowing of the first photoresist pattern 52 is reduced. Thus, when the second data pattern 174 is etched through a wet-etching process, a portion of each of the first to the third data patterns 171, 174 and 179, which is over-etched, may be relatively small. Thus, a portion of each of the first and the second n⁺ amorphous silicon layers 161 and 164, which is exposed, may be relatively small.

The first photoresist pattern 52 is removed, and an exposed portion of the second n⁺ amorphous silicon layer 164 is removed through a dry-etching process.

Referring to FIGS. 24 to 26, a protecting layer 180 is formed to cover the data line 171, the drain electrode 175 and the gate insulating layer 140.

The protecting layer 140 is etched through a photo-lithography process to form a plurality of contact holes 181,182, 183 a, 183 b and 185.

Referring to FIGS. 5 to 7, a transparent conductive material, such as ITO, IZO, etc., is deposited on the protecting layer 140 through a sputtering process and is patterned to the pixel electrode 191, the contact assistants 81 and 82 and the overpass 83.

EFFECT OF THE INVENTION

According to the above, a photoresist composition has a relatively high heat-resistance. Thus, when a photoresist film formed using the photoresist composition is heated, a profile variation of the photoresist film is relatively small. Therefore, a design margin may be increased, and a skew may be reduced.

Furthermore, a residual photoresist film has a uniform thickness. Thus, a short circuit and/or an open defect in a TFT substrate may be reduced. 

1. A photoresist composition comprising: about 100 parts by weight of resin mixture including novolak resin and acryl resin; and about 10 parts to about 50 parts by weight of naphthoquinone diazosulfonic acid ester.
 2. The photoresist composition of claim 1, wherein a weight-average molecular weight of the novolak resin is no less than about 30,000.
 3. The photoresist composition of claim 1, wherein the acryl resin is a copolymer that is obtained by polymerizing at least two selected from the group consisting of methyl methacrylate, ethyl methacrylate, methacrylic acid, styrene, benzyl acrylate and acrylic acid.
 4. The photoresist composition of claim 3, wherein a weight-average molecular weight of the acryl resin is no less than about 20,000.
 5. The photoresist composition of claim 4, wherein a content of the acryl resin is about 1% to about 15% by weight based on a total weight of the resin mixture.
 6. The photoresist composition of claim 1, further comprising an organic solvent.
 7. The photoresist composition of claim 6, wherein the organic solvent comprises at least one selected from the group consisting of propylene glycol monomethyl ether acetate and benzyl alcohol.
 8. A method of manufacturing a thin-film transistor substrate, the method comprising: forming a gate line on a base substrate, sequentially forming a gate insulating layer, a semiconductor layer and a data layer on the gate line and the base substrate; coating a photoresist composition on the data layer to form a photoresist film, the photoresist composition comprising about 100 parts by weight of resin mixture including novolak resin and acryl resin and about 10 parts to about 50 parts by weight of naphthoquinone diazosulfonic acid ester; patterning the photoresist film to form a photoresist pattern; firstly etching the data layer by using the photoresist pattern as a mask; etching the semiconductor layer by using an etched data layer; heating the photoresist pattern; and secondly etching the data layer by using a heated photoresist pattern as a mask.
 9. The method of claim 8, wherein a weight-average molecular weight of the novolak resin is no less than about 30,000.
 10. The method of claim 8, wherein a weight-average molecular weight of the acryl resin is no less than about 20,000.
 11. The method of claim 10, wherein a content of the acryl resin is about 1% to about 15% by weight based on a total weight of the resin mixture. 